Method for metalizing surfaces



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Patented Dec. 6, 1938 UNITED STATES METHOD FOR METALIZING SURFACES Eugen Mall, Stuttgart-Bad Cannstatt, and Waltcr Dorn, Stuttgart, Germany, assignors to Robert Bosch Gesellschaft mit beschri'mkter Haftung, Stuttgart, Germany No Drawing. Application March 17, 1937, Serial No. 131,532. In Germany March 30, 1936 13 Claims.

The invention relates to a method for metalizing surfaces by the purely thermal vaporization of metal in vacuo, in which the metal to be vaporized is heated in an evacuated vessel until it vaporizes, and the vapour is also precipitated in vacuo directly on the surface to be metalized. In this method in order to keep certain places on the surfaces to be metalized free from the deposition of metal, stencils have hitherto been employed to cover the surfaces at the places in question. Such stencils have the drawback that they also become coated withthe metal, so that the places left free by the stencils increase in size in course of time. It is thereforenecessary to change the stencils very frequently. In a continuous vaporizing method, in which metal-free and metalized places alternately succeed each other on a running band, the stencils have also the drawback that they must be arranged to run with the surface to be treated with vaporized metal.

According to the invention, the places to be kept free from metal are made in a substantially simp'er manner by their being covered before the metalizing with a substance, and which on heating in vacuo produces vapours. found that no metal precipitate is formed at such places. This is to be ascribed to the very hot molecules of metal vapour when vaporizing in vacuo liberating vapours from the substance applied at the places to be kept free from metal, which form a cushion against the penetration of the molecules of metal vapour;

The substance applied at the places to be kept free from metal is preferably in a liquid or semiliquid state.

As substances for preventing the precipitation of metal, hydrocarbons or hydrocarbon-like substances come principally in question. Greases and oils have been found very suitable. Halogen derivatives of the hydrocarbons, and further, alcohols, such for instance as glycerine, as well as resins, waxes, paraiiins and other organic substances, are however also suitable.

As for example in the case of grease, even the slightest traces of grease sufllce to prevent a deposit of the metal, the desired end can even be obtained with extremely thin layers or films of grease. The use of very thin layers is especially advisable, because thereby the edges of the layer are prevented from running and producing metal edges on the surface which are blurred.

For the technical production of the metal deposit while leaving certain places free, the precipitation inhibiting layer is applied to the surface to be metalized by printing or impressing it thereon. Any desired design can be obtained by this means in the metal layer in the simplest way, either by printing the design itself, in which case It has been.

the design copy remains free from metal, or by printing with a negative of the design whereby then the design itself is formed as-the metal deposit.

For the printing, not only the oils customary in printing, but also any other oil can be employed. Where it is desired to obtain very sharp edges, substances are preferably used whose surface tension is small at the temperatures employed, so that the edges do not become indistinct. Besides oils, greases, such for instance as petroleum jelly, and also resins and waxes or other organic substances may be used in the very thinnest layers for the printing.

If it is a question of metalizing bands or strips, for instance paper bands, one can for example, when using a very thin grease layer, first print the paper of a whole roll with the design in grease, and wind it up again, without the nonprinted parts thereby becoming greasy. The roll is then introduced into the vaporizing apparatus, the strip or band unwound from the roll, led past the vaporizing nozzle, and again wound up.

In cases where it is desired to get sharp metal edges, it is however better to do the printing'or impressing in the vacuumized vaporizing apparatus directly before the vaporizing, so that the grease has no time for its edges to become blurred.

The method is applicable for imprints or impressions of all kinds, thus for instance for advertising purposes on wrapping paper, or for similar purposes.

Further, it is very suitable for making metalized paper, such as can be employed for the construction of electrostatic condensers. By markings according to definite paper lengths, made for example with grease, metal-free marks can be provided in the manufacture of metalized paper, which subsequently, when assembling a condenser, give an indication of the wound up effective length of the paper. As in these condensers the metalized paper must usually have an edge free from metal, this edge may also be made by greasing or by applying any other precipitation-inhibiting substance, before the vaporizing.

The method described may also be used for the manufacture of condensers in which the metal deposit is applied to plates of mica or plates of a ceramic material. In this case, the places on the plates that are to be kept clear of metal are covered with the substances mentioned before the metalizing operation.

The method is also suitable for the manufacture of resistances. If, for example, thin layers of metal are applied to strips of insulating ma.- terial by vaporizing metal, the metal coating of the strip represents an ohmic resistance. This resistance can be increased by the metal layer running in meandering form on the strip or band. Forthis purpose, it is only necessary to print the band in meandering form w;th a precipitation inhibiting substance, such for instance as grease, before the vaporization, so as to cover those places which are to remain free from metal in the vaporizing. Paper bands metalized in meanders in this way can be rolled up into rolls, and very useful ohmic resistances for electro-technical purposes are thus ozained which are excellent-h adapted, for exar ole, for combination of resistances and capacities.

Electrical disc coils may also be made in a corresponding way. It is only necessary to make longitudinal stripes, for instance with grease, on a strip of insulating material. On the succeeding vaporizing, metal stripes are produced between the grease strips and on the winding up of the paper, form disc coil windings, which can be connected together in parallel, or, for exampie for producing very high voltages, in series.

The method described is also suitable for making cinematograph films when the picture to be projected is applied to a transparent film band in the form of a met :11 grid or screen. The places left free between he points of the grid are first imprinted with a precipitation inhibiting substance, such as grease. The film is then treated with metal vapour. Pictures made in this way have the advantage that the metalized opaque points strongly reflect the light and do not absorb it, like the black places in the present films do. When however less absorption takes place, the film is less strongly heated during the projection.

The method described can also be employed for sound-film records, by causing for example an oil-bearing member preferably of flexible material, to oscillate with light friction on the film band to correspond to the recorded sound oscillations, and thereby mark a touch of oil on the film band running past, the limits of which vary corresponding to the sound oscillations. After this recording, the band is developed by metal vaporization, and can then be employed in known manner with incident or transmitted light for the sound reproduction.

We declare that what we claim is:

l. A method of metalizing surfaces by the thermal vaporization of metal in vacuo comprising applying to a portion of the surface a thin coating of a precipitation-inhibiting substance liberating vapours when heated in vacuo, and then subjecting the surface to said metalizing operation to precipitate metal on the uncoated portion of said surface.

2. A method of metalizing surfaces by the thermal vaporization of metal in vacuo comprising applying to a portion of the surface a thin coatin" of a precipitation-inhibiting substance in a uid or semiliquid condition which liberates vapours on heating in vacuo, and then subjecting the surface to said inetalizing operation to preate metal on the uncoated portion of said surface.

3. A method of metalizing surfaces by the thermal varxirization of metal in vacuo comprisine applying to a portion of the surface a thin coatin of a hydrocarbon or hydrocarbon-like substance and then subjecting the surface to said inctaiizing operation to precipitate metal on the uncoated portion of said surface.

4. A method of metalizing surfaces by the thermal vaporization of metal in vacuo comprising applying to a portion of the surface a thin coating of a grease or oil, and then subjecting the surface to said metalizing operation to precipitate metal on the uncoated portion of said surface.

5. A method of metalizing surfaces by the thermal vaporization of metal in vacuo comprising applying to a portion of the surface a, thin film-like coating of an organic substance liberating vapours when heated in vacuo, and then subjecting the surface to said metalizing operation to precipitate metal on the uncoated portion of said surface.

6. A method of metalizing surfaces by the thermal vaporization of metal in vacuo comprising a-ppTying to a portion of the surface a thin coating of a precipitation-inhibiting substance of low surface tension at the temperature of treatment and liberating vapours when heated in vacuo, and then subjecting the surface to said metalizing operation to precipitate metal on the uncoated portion of said surface.

7. A method of metalizing surfaces by the thermal vaporization of a metal in vacuo, comprising printing a portion of the surface in vacuo with a vaporizable precipitation inhibiting substance, and then subjecting the surface to said metalizing operation to precipitate metal on the unprinted portion of said surface.

8. A method of metalizing strips or bands which consists in printing a portion of the surface of the strips or bands with a vaporizable substance inhibiting precipitatlon, and then treating said bands or strips with a metal vapour to precipitate metal on the unprinted portion thereof.

9. A method of manufacturing metalized pa.- pers which are provided with a design, picture or legend, comprising printing the design picture or legend on the paper in a vaporizable precipitation inhibiting substance, and thereupon metalizing the portion of the paper not covered thereby by thermal vaporization of metal in vacuo.

10. A method of manufacturing metalized papers which are provided with a design picture or legend comprising printing, all the paper except the design picture or legend with a vaporizable precipitation inhibiting substance, and thereupon metalizing the portion of the paper not covered thereby by thermal vaporization of metal in vacuo.

11. Method of making a band or strip or insulating material coated with metal, for example, paper for roll condensers comprising applying a thin coating of a vaporizable precipitation inhibiting substance at spaced points along said band or strip and then metalizing the uncoated portions of the material by thermal vaporization of metal in vacuo.

12. A method for thamanufacture of dielectric condensers comprising applying to at least one edge of a strip of paper or the like a thin coating of a vaporizable precipitation inhibiting substance and then metalizing the uncoated portion of the paper by thermal vaporization of metal in vacuo.

13. A method for the manufacture of metallic reactances comprising applying a thin coating of a vaporizable precipitation inhibiting substance in meandering form to a portion of the surface of an insulating material and then metalizing said insulating material by thermal vaporization of metal in vacuo whereby the metal is deposited on the uncoated portion of said insurating material in meandering form.

EUGEN MALL. WALTER DORN. 

